Elevated ε-(γ-glutamyl)lysine in human diabetic nephropathy results from increased expression and cellular release of tissue transglutaminase

Introduction: Diabetic nephropathy (DN) is the leading cause of chronic kidney failure, however the mechanisms underlying the characteristic expansion of the extracellular matrix (ECM) in diabetic kidneys remain controversial and unclear. In non-diabetic kidney scarring the protein crosslinking enzyme tissue transglutaminase (tTg) has been implicated in this process by the formation of increased ε-(γ-glutamyl)lysine bonds between ECM components in both experimental and human disease. Studies in db/db diabetic mice and in streptozotocin-treated rats have suggested a similar mechanism, although the relevance of this to human disease has not been addressed. Methods: We have undertaken a retrospective analysis of renal biopsies from 16 DN patients with type 2 diabetes mellitus using an immunohistochemical and immunofl uorescence approach, with tTg and ε-(γ-glutamyl)lysine crosslink quantified by confocal microscopy. Results: Immunofl uorescent analysis of human biopsies (confocal microscopy) showed increases in levels of tTg (+1,266%, p <0.001) and ε-(γ-glutamyl)lysine (+486%, p <0.001) in kidneys with DN compared to normal. Changes were predominantly in the extracellular periglomerular and peritubular areas. tTg staining correlated with e-(?-glutamyl)lysine (r = 0.615, p <0.01) and renal scarring (Masson's trichrome, r = 0.728, p <0.001). Significant changes in e-(?-glutamyl)lysine were also noted intracellularly in some (=5%) tubular epithelial cells. This is consistent with cells undergoing a novel transglutaminase-mediated cell death process in response to Ca influx and subsequent activation of intracellular tTg. Conclusion: Changes in tTg and ε-(γ- glutamyl)lysine occur in human DN. Cellular export of tTg may therefore be a factor in the perpetuation of DN by crosslinking and stabilisation of the ECM, while intracellular activation may lead to cell death contributing towards tubular atrophy. Copyright © 2004 S. Karger AG, Basel.

Low protein diet fed exclusively during mouse oocyte maturation leads to behavioural and cardiovascular abnormalities in offspring

Early embryonic development is known to be susceptible to maternal undernutrition, leading to a disease-related postnatal phenotype. To determine whether this sensitivity extended into oocyte development, we examined the effect of maternal normal protein diet (18% casein; NPD) or isocaloric low protein diet (9% casein; LPD) restricted to one ovulatory cycle (3.5 days) prior to natural mating in female MF-1 mice. After mating, all females received NPD for the remainder of gestation and all offspring were litter size adjusted and fed standard chow. No difference in gestation length, litter size, sex ratio or postnatal growth was observed between treatments. Maternal LPD did, however, induce abnormal anxiety-related behaviour in open field activities in male and female offspring (P <0.05). Maternal LPD offspring also exhibited elevated systolic blood pressure (SBP) in males at 9 and 15 weeks and in both sexes at 21 weeks (P <0.05). Male LPD offspring hypertension was accompanied by attenuated arterial responsiveness in vitro to vasodilators acetylcholine and isoprenaline (P <0.05). LPD female offspring adult kidneys were also smaller, but had increased nephron numbers (P <0.05). Moreover, the relationship between SBP and kidney or heart size or nephron number was altered by diet treatment (P <0.05). These data demonstrate the sensitivity of mouse maturing oocytes in vivo to maternal protein undernutrition and identify both behavioural and cardiovascular postnatal outcomes, indicative of adult disease. These outcomes probably derive from a direct effect of protein restriction, although indirect stress mechanisms may also be contributory. Similar and distinct postnatal outcomes were observed here compared with maternal LPD treatment during post-fertilization preimplantation development which may reflect the relative contribution of the paternal genome. © Journal compilation © 2008 The Physiological Society.